Automatic waistrest adjusting device for office chairs

ABSTRACT

An automatic waistrest adjusting device for office chairs includes a waistrest combined with the bottom of a backrest, and the waistrest comes with a design of connecting a curved flexible metal plate and making use of whose flexibility to suspend the bottom of the waistrest that can be turned flexibly with a user&#39;s waist to achieve an ergonomic stepless angular adjustment to allow the user&#39;s waist to lean at the most comfortable position. The waistrest adjusting device combines the waistrest and the backrest by simple components and assembling method, and achieves the effects of preventing poor performance and quality caused by an elastic fatigue and extending the use life.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a waistrest adjusting device for office chairs, and more particularly to a waistrest adjusting device with a structure that connects a curved flexible metal plate to the bottom of a backrest for automatically turning and adjusting the angle of a waistrest.

(b) Description of the Related Art

According to U.S. Pat. No. 7,303,232, shown in FIGS. 1A and 1B and filed by the applicant of the invention, a “BACKREST ADJUSTING DEVICE FOR OFFICE CHAIRS” includes a back frame 10. A waistrest 12 is mounted at the center 11 of the back frame 10. The waistrest 12 is flexibly moved back and forth within the center 11 of the back frame 10 by means of two pivots and springs positioned within a tube body 15. In this way, an angular adjustment is achieved.

According to U.S. Pat. No. 6,843,530, a “MULTI-STAGE BACKREST ASSEMBLY” includes a back plate positioned on a support frame. A waist plate is mounted at the bottom of the back plate by use of a V-shaped support bar. An elastic swivel device is mounted at the other end of the V-shaped support bar. A mounting shaft and a torsion spring are employed to achieve the angular adjustment when the waist rests thereon.

However, most of the conventional waistrest adjusting devices generally employ a spring for providing an elastic force for extension/contraction or an angular change. Regardless of a compression spring or a torque spring, the performance of the conventional waistrest adjusting device may be affected since the spring becomes elastically fatigue easily, particularly to the flexibility of the adjustment and the comfortability of an application. Furthermore, the spring is installed on a shaft element, higher material and assembling costs are incurred, and the installed spring and shaft elements may produce frictional noises after a long time of use. Obviously, the conventional waistrest adjusting device requires improvements.

SUMMARY OF THE INVENTION

Therefore, a primary object of the present invention is to provide an automatic waistrest adjusting device for office chairs for elastically adjusting an office chair with a user's waist according to the position of a human waist to achieve an ergonomic stepless angular adjustment of the office chair and provide the most comfortable leaning condition for an individual's waist.

Another object of the present invention is to provide an automatic waistrest adjusting device for office chairs that combines a waistrest and a backrest by simple components and assembling method to achieve high applicability and excellent elastic fatigue resistance to extend the using life.

In order to achieve the above-mentioned objects, the invention includes:

a) a seat, having a chair leg disposed at the bottom of the seat;

b) a stand, with the bottom pivotally coupled to a rear side of the seat;

c) a backrest, disposed at the front of the stand, and having a framework and an external cover installed onto the framework; and

d) a waistrest, disposed at the bottom of the framework of the backrest,

wherein one or more upper installation notches are formed at the bottom of the backrest framework, and one or more upper positioning holes are formed in a vertical direction from a surface of the framework to the upper installation notch; wherein the waistrest includes an external frame and an external cover installed onto the external frame, and a lower installation notch and a corresponding lower positioning hole are formed at the top of the external frame and opposite to the upper installation notch; and wherein at least one curved flexible metal plate, coupled between the backrest framework and the waistrest external frame, and having an upper fixing surface formed at an upper end portion and opposite to the upper installation notch of the framework, and an upper locking hole formed on the upper fixing surface and at a position opposite to the upper positioning hole and fixed by an upper bolt, and a lower fixing surface is formed at a lower end portion and opposite to the lower installation notch, and a lower locking hole is formed on the lower fixing surface and at a position opposite to the lower positioning hole and fixed by a lower bolt, and an n-shaped curve body is formed between the upper and lower fixing surfaces, such that after the n-shaped curved body is locked to the upper and lower installation notches by the upper and lower fixing surfaces respectively, the n-shaped curved body is situated at a gap formed between the bottom of the backrest framework and the top of the waistrest external frame, and whose elasticity makes the top side of the waistrest as a rotational connecting end to suspend the bottom in the air to achieve an ergonomic stepless angular adjustment

Based on the above-mentioned configuration, the waistrest in accordance with the invention is displaceable up and down for height-adjustment with the movement of the backrest, thereby achieving the best ergonomic operation state.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are an exploded view and a perspective view of a backrest adjusting device for office chairs respectively as disclosed in U.S. Pat. No. 7,303,232;

FIG. 2 is a perspective view of the present invention;

FIG. 3 is a perspective view of a chair back without installing an external cover of the present invention;

FIG. 4 is an exploded view of a chair back of the present invention;

FIG. 5 is a perspective view of a chair back of the present invention;

FIG. 6 is a perspective view of a curved flexible metal plate of the present invention;

FIG. 7 is a cross-sectional view of the present invention with installing a curved flexible metal plate;

FIG. 8 is a perspective view of the present invention viewed from another angle; and

FIG. 9 is a schematic view of using the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIGS. 2 to 9 for a waistrest adjusting device for office chairs in accordance with a preferred embodiment of the present invention, the waistrest adjusting device comprises: a seat 20, having chair legs 21 installed at the bottom of the seat 20; a stand 30, with the bottom pivotally coupled to a rear side of the seat 20; a backrest 40, disposed at the front of the stand 30, and having a framework 44 and an external cover 47 installed onto the framework 44, wherein the external cover 47 of this preferred embodiment is made of meshed cloth, but the present invention is not limited to such arrangement only; a waistrest 50, disposed at the bottom of the of framework 44 of the backrest 40. The above-mentioned techniques are involved in prior arts, therefore, no more details are described here.

The present invention is characterized in that one or more upper installation notches 41 with opening aligned downward are formed at the bottom of the framework 44, and one or more upper positioning holes 42 are formed along the vertical direction from a surface of the framework 44 to the upper installation notch 41.

The waistrest 50 includes an external frame 54 and an external cover 55 installed onto the external frame 54, a lower installation notch 51 with opening aligned upward and formed at the top of the external frame 54 and opposite to the upper installation notch 41, and a corresponding lower positioning hole 52.

In this preferred embodiment, two curved flexible metal plates 60 are coupled between the backrest framework 44 and the waistrest external frame 54, and an upper end portion opposite to the upper installation notch 41 of the framework 44 constitutes an upper fixing surface 61, and the upper fixing surface 61 opposite to the upper positioning hole 42 has an upper locking hole 611 formed thereon and fixed by an upper bolt 43, and a lower end portion opposite to the lower installation notch 51 constitutes a lower fixing surface 62, and the lower fixing surface 62 opposite to the lower positioning hole 52 has a lower locking hole 621 formed thereon and fixed by a lower bolt 53. In addition, an n-shaped curved body 63 is formed between the upper and lower fixing surfaces 61, 62, such that after the n-shaped curved body 63 is secured onto the upper and lower installation notches 41, 51 by the upper and lower fixing surfaces 61, 62 respectively, the n-shaped curved body 63 is disposed at a gap between the bottom of the backrest framework 44 and the top of the waistrest external frame 54, and its elasticity is provided for making the top of the waistrest 50 as a rotational connecting end, and the bottom side is suspended in the air to achieve the synchronous ergonomic stepless angular adjustment.

In this preferred embodiment, the curved flexible metal plate 60 is a steel plate having a specific elasticity. In a preferred embodiment, the gap S between the upper and the lower of the n-shaped curved body of the curved flexible metal plate is smaller than 3 cm, and the depths D between the front and the rear is greater than the gap S as shown in FIG. 7. The gap S is preferably between 0.5 cm to 1.5 cm. This design features a very good elasticity and a high elastic fatigue resistance of the curved flexible metal plate 60. Compared with the conventional torque spring, the curved flexible metal plate 60 of the present invention not only has excellent strength, but also has a long using life. In addition, the installation is convenient, and the invention requires no rotating shaft, and thus is free of the shortcoming of having any frictional noise produced by the torque spring easily. More importantly, when a user's waist leans against the chair back, the n-shaped curved body 63 can be used as a pivoting portion for rotating the chair back to the most comfortable angle automatically, and the using status is shown in FIG. 9.

In this preferred embodiment as shown in FIG. 4, the framework 44 of the backrest 40 is comprised of a front framework 44 a and a rear framework 44 b, and a transverse bar 45 is installed at the rear side of the framework 44, and the transverse bar 45 has two parallel longitudinal slide sleeves 46 displaceable on the positioning portion 32 of the stand 30 for adjusting the height of the backrest 40. The structure of the positioning portion 32 can be a ratchet operated with latch elements (not shown in the figure) in the longitudinal slide sleeves 46, but the latch structure is not the object of the present invention, and thus is not described here.

In addition, the external frame 54 of the waistrest 50 is comprised of a front frame 54 a and a rear frame 54 b, and the waistrest 50 is displaced with the backrest 40 up and down on the stand 30. A headrest 70 is installed at the top of the backrest 40, but the invention is not limited to such arrangement only.

In this preferred embodiment, the cross-section of the rear framework 44 b of the backrest 40 and the rear frame 54 b of the waistrest 50 are substantially U-shaped grooves 48, 56. The front framework 44 a and front frame 54 a are embedded in the U-shaped grooves 48, 56 respectively, and concave and convex connecting members 49, 57 of a joint of the two are used for combining the framework 44 and the external frame 54, or a further manufacture can be used instead.

With the aforementioned assembly, the present invention uses the design of connecting a curved flexible metal plate 60 and makes use of the characteristic of the flexibility of the metal plate 60 to suspend the bottom of the waistrest 50 in the air, and flexibly turn the chair to an angle with the user's waist to achieve an ergonomic stepless angular adjustment, so that the user's waist can lean against the chair back at the most comfortable position. In addition, the present invention can achieve the effects of combining the waistrest 50 and the backrest 40 by simple components and assembling method, preventing poor performance and quality caused by the elastic fatigue, and extending the using life.

Many changes and modifications in the above-described embodiments of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims. 

1. An automatic waistrest adjusting device for office chairs, comprising: a) a seat, having a chair leg disposed at the bottom of the seat; b) a stand, with the bottom pivotally coupled to a rear side of the seat; c) a backrest, disposed at the front of the stand, and having a framework and an external cover installed onto the framework; and d) a waistrest, disposed at the bottom of the framework of the backrest, wherein one or more upper installation notches are formed at the bottom of the backrest framework, and one or more upper positioning holes are formed in a vertical direction from a surface of the framework to the upper installation notch; wherein the waistrest includes an external frame and an external cover installed onto the external frame, and a lower installation notch and a corresponding lower positioning hole are formed at the top of the external frame and opposite to the upper installation notch; and wherein at least one curved flexible metal plate, coupled between the backrest framework and the waistrest external frame, and having an upper fixing surface formed at an upper end portion and opposite to the upper installation notch of the framework, and an upper locking hole formed on the upper fixing surface and at a position opposite to the upper positioning hole and fixed by an upper bolt, and a lower fixing surface is formed at a lower end portion and opposite to the lower installation notch, and a lower locking hole is formed on the lower fixing surface and at a position opposite to the lower positioning hole and fixed by a lower bolt, and an n-shaped curved body is formed between the upper and lower fixing surfaces, such that after the n-shaped curved body is locked to the upper and lower installation notches by the upper and lower fixing surfaces respectively, the n-shaped curved body is situated at a gap formed between the bottom of the backrest framework and the top of the waistrest external frame, and whose elasticity makes the top side of the waistrest as a rotational connecting end to suspend the bottom in the air to achieve an ergonomic stepless angular adjustment.
 2. The automatic waistrest adjusting device for office chairs as recited in claim 1, wherein the curved flexible metal plate is a steel plate.
 3. The automatic waistrest adjusting device for office chairs as recited in claim 2, wherein the gap S between the upper and the lower of the n-shaped curved body of the curved flexible metal plate is smaller than 3 cm, and the depths D between the front and the rear is greater than the gap S.
 4. The automatic waistrest adjusting device for office chairs as recited in claim 3, wherein the gap S is between 0.5 cm to 1.5 cm.
 5. The automatic waistrest adjusting device for office chairs as recited in claim 1, wherein the framework of the backrest comprises a front framework, a rear framework, a transverse bar installed at the rear side of the framework, and two parallel longitudinal slide sleeves installed on the transverse bar and displaceable to be up and down on the positioning portion of the stand for adjusting the height of the backrest.
 6. The automatic waistrest adjusting device for office chairs as recited in claim 5, wherein the cross-section of the rear framework is substantially a U-shaped groove, and the front framework is embedded into the U-shaped groove and latched and fixed by using concave and convex combining members at a joint of the front framework and the U-shaped groove.
 7. The automatic waistrest adjusting device for office chairs as recited in claim 5, wherein the external frame of the waistrest is comprised of a front frame and a rear frame, and the waistrest is displaced with the backrest up and down on the stand.
 8. The automatic waistrest adjusting device for office chairs as recited in claim 7, wherein the cross-section of the rear frame is a substantially U-shaped groove while the front frame are embedded in the U-shaped groove, and concave and convex connecting members are used for combining the rear frame and the front frame. 